I. Equine Herpesviruses
There are four known equine herpesvirus types (O'Callaghan, D. J. et al, In: The Herpesviruses, Ed. Roizman B., Plenum Press, New York, 2:215-318 (1983); Studdert, M. J. et al, Science, 214:562-564 (1981); and Studdert, M. J. et al, Arch. Virol., 91:375-381 (1986)). Equine Abortion Virus, also known as Equine Herpesvirus Type 1 (hereinafter "EHV-1", is a major cause of respiratory disease and abortion in horses. Equine Herpesvirus Type 2 is a ubiquitous, slowly growing cytomegalovirus which is not identified with any known disease syndromes in horses. Equine Herpesvirus Type 3 is the agent of genital exanthema of mares and stallions. Equine Herpesvirus Type 4 causes recurrent respiratory disease which can impair racing performance. Each of these equine herpesvirus types are fundamentally distinct in terms of associated clinical symptoms, histopathology serology, nucleic acid homology, and epidemiological patterns.